Non-human behavior-genetic research has traditionally relied heavily on inbred mice as subjects for study. While recognizing the value of these animals for experimentation, non-domesticated or wild mice of the species Mus musculus also offer unique opportunities for research. Electrophoretic studies have repeatedly found that populations of such mice located quite close to one another typically differ to a remarkable extent in terms of the proportion of the various alleles present. If this is the case, it should be possible to demonstrate behavioral variation as well. To test this possibility, 320 mice representing eight different but adjacent farm populations (40 mice per farm) will be run in a battery of five standard behavior genetic tests. To eliminate environmental sources of variation, it will be necessary to test the laboratory reared offspring of wild caught mice, rather than the original animals. Statistically significant differences will demonstrate the existence of genetically determined behavioral distinctiveness at a relatively low level of population divergence. Also, it is anticipated that the project will promote the study of natural populations as well as laboratory strains of house mice.